The present application is related to devices and methods for promoting blood circulation to the heart muscle. Specifically, the present invention is related to percutaneous myocardial revascularization (PMR) devices and methods for forming multiple channels in the myocardium.
A number of techniques are available for treating cardiovascular disease such as cardiovascular by-pass surgery, coronary angioplasty, laser angioplasty and atherectomy. These techniques are generally applied to by-pass or open lesions in coronary vessels to restore and increase blood flow to the heart muscle. In some patients, the number of lesions are so great, or the location so remote in the patient vasculature that restoring blood flow to the heart muscle is difficult. Percutaneous myocardial revascularization (PMR) has been developed as an alternative to these techniques which are directed at by-passing or removing lesions.
Heart muscle may be classified as healthy, hibernating and xe2x80x9cdeadxe2x80x9d. Dead tissue is not dead but is scarred, not contracting, and no longer capable of contracting even if it were supplied adequately with blood. Hibernating tissue is not contracting muscle tissue but is capable of contracting, should it be adequately re-supplied with blood. PMR is performed by boring channels directly into the myocardium of the heart.
PMR was inspired in part by observations that reptilian hearts muscle is supplied primarily by blood perfusing directly from within heart chambers to the heart muscle. This contrasts with the human heart, which is supplied by coronary vessels receiving blood from the aorta. Positive results have been demonstrated in some human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing from within a heart chamber through patent channels formed by PMR to the myocardial tissue. Suitable PMR channels have been burned by laser, cut by mechanical means, and burned by radio frequency current devices. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound.
What remains to be provided are improved methods and devices for increasing blood perfusion to the myocardial tissue. What remains to be provided are methods and devices for increasing blood flow to myocardial tissue through controlled formation of channel patterns in the myocardium.
The present invention includes devices and methods for creation of multiple holes in the myocardium of a human heart for percutaneous myocardial revascularization. A pattern of holes is optimally created extending from healthy tissue to hibernating tissue, thereby increasing the supply of blood to hibernating heart muscle tissue. Creating a controlled pattern of channels rather than simply a plurality of channels of unknown location can be accomplished using various methods and devices. Holes can be considered the space left after a volumetric removal of material from the heart wall. Channels have a depth greater than their width and craters have a width greater than their depth.
One method includes marking a first location in the heart muscle wall with a radiopaque marker, then positioning a radiopaque cutting tip relative to the radiopaque marker using fluoroscopy and cutting channels in the myocardium where appropriate. Suitable markers can be secured to the endocardium mechanically with barbs or pigtails or injected into the myocardium. Suitable channel patterns include lines, arrays, and circular clusters of channels.
Another method includes injecting radiopaque material into the newly formed channels, thereby marking the positions of the channels already formed. The radiopaque material should be held in place with polymeric adhesives for the duration of the treatment. The channels formed can be viewed under fluoroscopy using this method. The marker can remain throughout the procedure or only long enough to record the position for mapping.
Yet another method can be accomplished by providing a myocardial channel forming device having an anchoring member, a treatment member with a cutting tip, means for rotating the cutting member about the anchoring member, and means for controlling the radial displacement of the cutting tip from the anchoring member. The anchoring member can be implanted in a heart chamber wall using a pigtail, and the radial and rotational displacement of the cutting tip controlled to sequentially form a circular cluster of channels about the anchoring member. The circular cluster preferably includes both healthy and hibernating tissue areas, which can be mapped using conventional techniques. A variant of this technique utilizes a device having a spline and corresponding star shaft, which restricts the number of possible rotational angles and provide predictable arc rotations around the spline for the treatment member about the anchoring shaft.
Still another method utilizes a bundle of fibers within a sheath as the cutting device. Preferred fibers are formed of Nitinol wire and carry radio frequency current to effect burning channels in the myocardium. Optical fibers carrying laser light for burning are used in another embodiment. The splay of fibers out of the distal end of the sheath can be controlled by controlling the bias of the fibers. The bias of the fibers can be controlled by utilizing shape memory materials, such as Nitinol wire. The splay of fibers can also be controlled by controlling the length of fiber exposed at the distal end, by controlling the retraction of the sheath over the fibers.
A variant device utilizes a magnetically responsive anchoring member, which can be pulled against the heart wall by an external magnetic force. The heart wall can have movement lessened during this procedure and other procedures generally, by inserting a catheter having a magnetically responsive distal region into a coronary artery. Force can be brought to bear upon the heart wall region having the catheter disposed within by applying a magnetic force on the catheter. The applied force can exert a pulling force on the catheter, reducing movement of the beating heart wall in that region.
Another device includes an outer positioning tube having several side channels in the distal region and means for securing the distal region against movement within the heart chamber. One securing means includes a suction orifice near the distal end supplied with vacuum by a vacuum lumen extending the length of the outer tube. Another securing means includes a magnetically responsive portion of the outer tube. The suction orifice can be secured to the heart chamber wall by applying vacuum and the magnetically responsive portion can be forced into the chamber wall by applying an external magnet field. The inner tube can contain an intermediate guide tube and the guide tube can contain an inner PMR cutting wire with a arcuate biased distal region. As the arcuate distal region is moved through the outer tube distal region and over the side channels, the PMR wire distal region can extend through a side channel and to the heart chamber wall. The PMR wire can be moved past undesired side holes by rotating the wire such that the arcuate wire region is oriented away from the side holes.
Another device includes a tube-in-a-tube configuration, having an outer tube disposed about an intermediate tube disposed about an inner PMR cutting probe. The inner PMR probe can be preformed to have a distal region arcuate or angled bias, bent away from the longitudinal axis of the probe. The PMR probe distal region can extend through a side channel in the distal region of the intermediate tube and is slidable within the intermediate tube, thereby exposing a varying length of distal PMR probe outside of the intermediate tube. The intermediate tube is slidably disposed within the outer tube which has an elongate slot to allow passage of the PMR probe therethrough. Thus, the radial extent or length of extending PMR probe can be varied by sliding the PMR probe within the intermediate and outer tubes, the longitudinal position of the PMR probe can be varied by sliding the intermediate tube within the outer tube, and the rotational position can be varied by rotating the outer tube from the proximal end. Varying the amount of a preformed, bent PMR probe extending from the intermediate tube can also change the longitudinal position of the PMR probe distal end.
Another device includes an elongate rod having a distal region secured to an outer collar, such that the outer collar can be pushed and pulled. The outer collar is slidably disposed over an intermediate tube. An inner PMR cutting probe is slidably disposed within the intermediate tube. The inner PMR probe and intermediate tube together have a distal region arcuate or bent bias or preform, such that distally advancing the outer collar over the intermediate tube straightens out the intermediate tube and proximally retracting the outer collar allows the arcuate bias or bend to be exhibited in the distal region shape of PMR probe and intermediate tube. The preform can exist in the PMR probe, intermediate tube, or both. The device includes means for anchoring the device to the ventricle wall. Circles or arcs of myocardial channels can be formed by rotating the outer tube, extending the inner PMR probe, and varying the amount of arc to form distal of the outer collar.
Yet another device includes an anchoring member and a positionable cryanoblative treatment tube. The treatment tube can be formed of metal and be either closed or open ended. In use, the device is anchored within a heart chamber and a cryogenic substance such a liquid nitrogen delivered through the tube and to the tube distal end. The liquid nitrogen can cause localized tissue death, bringing about the desired healing response. Still another device includes a plurality of splayed, cryanoblative tubes within a sheath. The tubes can be supplied with liquid nitrogen, which can be delivered through the tube lumens to the tube distal ends so as to cause localized myocardial tissue death at multiple sites substantially simultaneously.
In yet another embodiment, a catheter assembly is provided including a guide wire having a proximal end and a distal end. An expandable member, which may be a wire loop, is disposed at the distal end of the guide wire. The expandable member is moveable between a first position and a second position. In the first position, the member is collapsed to move through a lumen of a guide catheter. In a second position, the expandable member has a transverse diameter, with respect to the length of the guide wire, greater than the transverse diameter of the guide catheter lumen. An elongate catheter having a proximal end and a distal end is disposed on the guide wire. A therapeutic device is connected to the distal end of the catheter. The therapeutic device can be a needle, hypotube, electrode or abrasive burr to form holes or craters in the myocardium of the patient""s heart.